Measuring and controlling apparatus



. Nov. 22, 1938. I J. D. RYDER R-' 20,927

MEASURING AND CONTROLLING APPARATUS I oriihal Filed April 14; 1952 Fig. -1

INVENTOR hn D. Ryder.

- range in magnitude of the condition whilethe' recording or indicating means may be sensitive Reissuecl Nov. 22, 1938 John D. Ryder, South Euclid, Ohio, assignor to Bailey Meter Company, a corporation of Delaware Original No. 1,931,414, dated October 17, 1933,

Serial No. 605,269, Apr-i114, 1932. Application for reissue July 31, 1935, Serial No. 34,116

40 Claims. (Cl. 236-70) The present invention relates to apparatus for measuring anti/or controlling the magnitude of a variable and. particularly such variable condi tions as temperature, pressure, rate of fluid flow, etc., although the variable may be of any chemical, electrical, thermal, physical or other nature or characteristic.

According to the invention, I produce an electrical effect varying in known proportion to the magnitude of a variable condition whose magnitude or variation from predetermined value I de-' Such electrical effect may be a small force such as an electro-.

sire to measure or control.

motive force produced by a thermocouple and may be magnified to any desired degree to perform useful work. The electrical effect may be representative of the difference in magnitude of two independent variables whereby the magnitude of one 01 the independent variables may be determined and/ or controlled.

One object of the invention is to provide apparatus and arrangement of the character referred to wherein the deflections of a galvanometer or other sensitive device may be utilized in the control of amplified power to stop, start or reverse either direct current motorsor alternat -ing current motors, or the two simultaneously.

Another object of the invention is to provide for the simultaneous indication of the value of from, apredetermined value but also in the dea variable condition along with a control of the magnitude of the condition. I

A further object is to provide for alternately controlling and recording or indicating the magnitude of a variable condition, and wherein one result may be accomplished with a direct current motor and the other result with an alternating current motor.

A still further object relates to apparatus whereby the regulating means for control ofthe variable may be positioned over a predetermined to variations in magnitude of the condition of greater or lesser extent.

Still another object is to eilect the control of the variable condition, not only in accordance with'the departure in magnitude of the variable parture in value for any period of time from the value at a predetermined period of time.

Still another object is to arrange for the de- 3 ilecting or sensitive instrumenhsuch as a galvanometer, tobe made less sensitive to variations in electrical potential over a predetermined range than over another predetermined range.

Still further objects of the invention will become apparent from the drawing and the description relating thereto in connection with preferred embodiments which I have chosen as representative and wherein variable temperature in the operation of a heating furnace is measured and controlled either simultaneously or successively.

Inthe drawing:

Fig. 1 is a diagrammatic arrangement of apparatusand electric circuit embodying the invention in connection with the measurement of a temperature of a furnace and the control simultaneously therewith and therefrom of supply of fuel to the said furnace.

Fig. 2 is a diagrammatic arrangement of apparatus and circuit embodying .a modification of the arrangement of Fig. 1.

Referring first to Fig. 1, I therein illustrate an embodiment -of my invention wherein the temperature of a metallurgical heating furnace l is measured for' instantaneous reading on an index and for recording upon a continuous record chart. Furthermore, from such temperature evaluation and its relationin magnitude to a predetemined value which is desirably to be maintained in the furnace, I effect a control of the supply of fuel fed to the furnace I through a burner 2 by throttling or controlling the throttled position of a valve 8 located in the fuel oil supply line before the burner 2. The air for combustion enters the furnace around the burner 2. At I indicate a thermocouple located sensitive to temperature within the furnace and which temperature is to be indicated and controlled.

Primarily, when there is a deviation in temperature within the furnace, a potential relation in the thermocouple circuit-is disturbed and from such lackof balance a periodically actuated ieeler mechanism cooperates with electrical magnification means for effecting the positioning simultaneously of an alternating current motor to advise the value of the temperature, and a directcurrent motor to control fuel admission to the effect of the thermocouple, sensitive to and representative of the temperature within the furnace, and where such amplification may be utilized for remotely or locallyrecording, indicating and/or controlling variable factors in the operation of the furnace.

I have illustrated the thermocouple l as having its hot junction located within the furnace. By

. the term. hot junction it is to be understood that I mean that-junction ofthe thermocouple which is exposed to the temperature it is desired to evaluate regardless of whether that temperature is of a greater or lesser magnitude than the room or reference temperature to which the other junction of the thermocouple circuit is normally exposed, and which I term for simplicity the cold junction.

The electrical efiect obtained through the thermocouple 4 indicative of variations in the temperature within the furnace, is utilized in a potentiometer circuit, as will be explained hereinafter, for positioning of the sensitive galvanometer. A mechanically periodically-actuated feeling device cooperates .with the galvanometer needle for the control upon departure of temperature from predetermined value, of thermionic or electron. discharge devices whereby the minute electrical efiect is amplified or magnified. The magnified effect then controls electromagnetic devices, such as motors, whicl; are utilized as amplified power means for positioning indicator andrecor'ding members of the temperature and. also positioning the control valve 3.

, I show at 5 a motor having opposed windings, 6 and I, connected in an alternating current circuit and oppose'dly wound in a manner such that when thewindings 6 and I are equally energized, a rotor 8 is not urged to rotation in either direction; but when the windings are unequally energized, rotationof the rotor 8 will occur in predetermined direction. Carried by the rotor 8 for angular positioning thereby, is an indicator arm 9 adapted to cooperate with an index Ill and comprising a marking means arranged to form a continuous record upon a chart H, driven at a uniform speed by a clock motor I2. The assembly comprising the motor 5 and indicating-recording means is adapted to advise the value of the temperature at which the thermocouple! is sensitive. g

Upon every change in temperature atthe thermocouple 4, I effect an angular displacement of the rotor 8 directly proportional to th'e'variation in the thermocouple potential through'sub- I stantially de-energiZing one or theother of the field windings 6, 11 in a 'manner to be explained.

Further responsive to temperature at the thermocouple I, connected for operation in parallel with the motor 5, I show a motor I3 for positioning in desired direction and amount the fuel control valve 3. The motor l3 has a spthrough the application thereto of equal opposing torques comprising: the alternate half cycles of an alternating current wave: the armature being Iii-"7 c ect d in an alternating current e'ir- -comprising a pulsating direct current in one direction, causes rotation in the desired direction.

' When the armature is rotating through the impulse of pulsating direct current in a given direction, and it is desired to stop rotation of the armature, I apply to the armature the other half of the alternating current wave whereby an equal opposing torque plus the counter E. M. F. is substantially instantaneously applied to the armature, effecting a substantially instantaneous stoppage of rotation thereof, 7 and whereafter the armature is not urged to rotation in either direction until one or the other of the half wave pulsating direct current forces is released.

The motor I3 is connected at one terminal directly with an alternating current power source l5 through a current limiting reactor I 6 of the closed core type, and at the other terminal in series with a pair of thermionic electron discharge devices l1, l8 opposedly connected in parallel with each other but as a pair in series between the power source I5 and the armature IS.

The reactor l6 allows full wave alternating current to be impressed across the armature IS without burning the same. While the electron discharge devices l1, l8 each pass to the armature one half of the alternating current wave comprising a pulsating direct current and being opposedly connected in parallel when both of the devices are conducting, there is applied to the armature full wave alternating current. The present embodiment of my invention contemplates a control of the devices l'l, I8 for allowing either or both to be conducting whereby the motor [3 is allowed to rotate in desired direction or to be unurged to rotation. I

It will be observed that the arrangement is such that when temperature at the thermocouple 4 varies, an electromotive force of minute value will be set up in the thermocouple circuit which, through proper means to be hereinafter described, I amplify for the control of rotation in amount and direction of the motors 5 and I3 simultaneously and in parallel for indicating and recording thetemperature in the furnace, as well as controlling the fuel supply valve 3, to maintain such temperature substantially uniform.

In connection with the thermocouple 4 and the motors 5, I3, I utilize a single'galvanometer and feeler device whereby I periodically determine, through the departure 'of the galvanometer needie from neutral position, acha'nge in magnitude 'of'th'e temperature of the furnace, and upon finding that the needlehas departed in one (11- rection or the other from neutral position, I cause a' positioning of the rotor 8 or the motor l3 for indicating andrecording the new temperature and through the 'valve' 3 controlling the fuel supply to the furnacejto tend to return the temperature to predetermined value.

In the circuit'of the thermocouple 4 I utilize the well known zero balance or null method. In

swing a departure from balance and eifects indirectly a movement on the slide wire potenaccordance with this method, the potential def veloped by the thermocouple is balanced against ithe fall of potential through a portion of a slide wire potentiometer or resistance of known length and value per unit of length. Upon a changein potential developed by the thermocouple, a gal- Yvanometeri'n the circuit indicates by its needle effected. The physical position of the contact point of the slide wire potentiometer may be further utilized as\an indication of temperature equivalent to the potential across the thermocouple. 7

Such, in general, is the system which I employ. A constant drop in potential is maintained across the slide wire potentiometer resistance by means of a suitable current source and it is evident that the amount or length of resistance necessary to balance the potential generated by the thermocouple will then be proportional to that potential and may, by suitable calibration, be used to determine its magnitude and, correspondingly, the magnitude of the temperature to which the thermocouple is sensitive. In Fig. l I provide such a potentiometer circuit, essentially comprised of a current source battery I! connected in series with a slide wire potentiometer 20. A galvanometer, diagrammatically indicated as 2|, is connected in series with thermocouple 4 and they together span that part of thepotentiometer circuit between contact arm 20A and a variable resistance 22 later to be.described. The contact arm 20A comprises an extension of the indicator arm 9,

- insulated therefrom and adapted to frictionally 'angular positioning of the rotor 8.

engage along the slide wire resistance 20 upon When the difference in potential through that part of the potentiometer circuit between the arm 20A and the variable resistance 22 is equal to that developed by the thermocouple 4, the galvanometer needle 23 will remain stationary midway between two movable contacts 24 and 25 as shown.

Upon a variation in temperature within the furnace, resulting in a corresponding increase or decrease in the potential difference developed by the thermocouple 4, the galvanometer needle 23 will be deflected either to the right or to the left on the drawing an amount substantially proportional to the variation in temperature. Upon such a deflection'of' the 'galvanometer needle, periodically engagement will be made between the galvanometer needle and either -the contact 24 or the contact 25, with the result that rotation of the rotor I, and simultaneously of the rotor l3, will be effected in the proper direction to move the indicator 3 to read the new temperature, to position the fuel supply valve 3 foivariation in the supply of fuel, and to move the contact arm 20A along the slide wire resistance 20 until the difference of potential through that part of the potentiometer circuit between the contact arm 23A and the variable resistance 22 is again equal to that developed by the thermocouple. It is evident that the amount of movement of the arm 20A will then be proportional to the change in temperature within the furnace and according- 1y 2. true indication of the new temperature will be accomplished on the chart II, and relative to the index Ill, through movement of the indicator marker 9. Simultaneously, the supply of fuel to the furnace will have been varied an amount in direction whereby the heating of the furnace will be corrected to tend to return the temperature at the thermocouple 4 to predetermined desirable value.

.I show diagrammatically in the drawing the mechanism through whose agency I,- am enabled to periodically transmute the mechanical mamfestation of the galvanometer needle of changes in potential generated by the thermocouple con-,

nected thereto, into electrical manifestation-of constant magnitude, but which continue for an 20,927 i tiometer whereby a zero balance of potential is incrementof time proportional to the mechanical manifestation of the galvanometer needle.

This feeler mechanism is more generally described, illustrated and specifically claimed in my co-pending application, Serial No. 605,268, filed of even date herewith and having the same assignee. The electrical manifestation so obtained I then use to control' the energization of the motors 5 and I3.

Referring to the diagrammatic illustration of Fig. 1, members illustrated as scissor bars 23 and 21, both pivoted at 28, are periodically moved toward and away from each other by the agency of similar but oppositely positioned cams 29, '30 rigidly attached to a shaft 3| rotated at constant speed by a continuously operating motor 32. The scissor bars 26, 21 are provided at their lowermost ends with rollers, the one riding the surface of the cam 23 and the other the surface of the cam 30, andthe scissor bars further carry, respectively, the contacts 24, 25 insulated therefrom and from each other.

The galvonometer 21 as shown is of the suspended type and properly located relative to a permanent magnet in known manner. Normally, the needle 23 of the galvanometer is free to defleet, in accordance with the difference of potential generated by the source to which the galvanometer is connected and that portion of the potentiometer circuit spanned. Periodically, however, the needle 23 is clamped between a stationary portion 33 and a movable bar 34 which is reciprocated by means of a constantly revolving cam 35 secured to the shaft 3|. Thus, periodically upon each revolution of the'cam 35 the needle 23 will be clamped lightly between the stationary member 33 and the movable reciprocating bar 34, and for aportlon of each revolution of the cam 35.

Immediately after the needle 2'3 has been so clamped, the position of the earns 28, 30 relative to the cam 35, is such that the scissor arms 28,

21 move toward each other. When, as shown, the

galvanometer needle 23 is in mid-position, indithen the adjacent scissors arm will follow the periphery of the associated cam until the contact carried by the scissors arm reaches the needle.

Further motion of this scissors arm toward the other will then be prevented by the galvanometer needle and the engaged contact will remain in engagement with the needle until the scissors arm moved away. At a predetermined definite point in the outward travel of the scissors arms, the galvanometer needle 23 will be released from clamping engagement and be free todeflect either fur.- ther away or return toward the predetermined neutralposition'and until it is again clamped as the scissors arms travel toward each other on the next cam cycle. of revolution;

. is again picked up by the associated cam and l It is evident that by proper shapingof the cams 23, 30 the length of time the scissors arms are in contact with thene'edle 23, may be made direct- 1y proportional to the. amount of deviation of the needle from mid-position, which in turn is proportional to the diiferenc'e of the opposed potential. If desired, one of the'cams, for example 28, may be made of a different shape than the other cam, for example 20, whereby the galvanometer needle in one direction may be made difierent from that for the same amount of deflection of the galvanometer needle'in the opposite direction- It is further evident that the cams 29, may be made of any desired shape so that the length of engagement between the contacts carried by the scissors arms and the galvanometer needle will bear any desired functional relation to the amount of deviation from the neutral or mid-position of the galvanometer needle.

I utilize the feeling and clamping apparatus just described to produce an electrical effect bearing definite relation to the departure of the galvanometer needle from neutral position and for the control 01' operation of motors 5 and I3. Intermediary between the feeler apparatus and the motors mentioned and controlled by a mithe contact 24 or the contact 25, I interposel electron discharge devices or thermionic valves 11, I8 for controlling an amplified or substantially greater electrical force to be directly applied to the motors mentioned. Certain features of the motor control circuit including the electron discharge devices are described and claimed in my co-pending application; Serial No. 605,267 filed of even date herewith and having the same assignee. I will now explain the functioning of this apparatus in suillcient detail to be understandable in conjunction with the present application, although it will be understood that the arrangement is illustrated and described-in greater detail in the aforementioned co-pending application.

The galvanometer needle 23 is connected directly to one side of the alternating current source |5 through a suitable resistor 36. The discharge devices l8 are provided with anodes 31, 3B, grids 35, 40 and cathodes 4|, 42, respectively. A source of current for heating the cathodes 4|, 42 is provided by the secondaries of the transformers 43, '44 which are connected across the alternating current source I5. Devices l8 as previously mentioned are connected oppositely in parallel with each other; that is, the anode 37 is connected to the cathode 42, while the anode 38 is connected to the cathode 4|.

Grids 39, 40 are connected together and maintained at a -normal potential relation with respect to the cathodes 4|, 42 by suitable impedance devices herein shown as -resistors 36 and 45. The potential relation maintained by the resistors 36, 45- is such that during a half of the alternating current cycle, the device will transmit current through its output circuit, and during the alternate half of the alternating current cycle the device I8 will transmit current in-the opposite direction through its output circuit, Normally, therefore, an alternating currentiwill be impressed upon the motor 3 which iscon= nected across the power source 5 in. series with the parallel connected devices l3.

If one or the other of the devices 11, .|8 is not conducting, then .a pulsating direct current of one direction will beimpressed upon the mo tor l3'which will rotate-in predetermined direction; Control of' the devices n; i8 as to whether or not they are individually conducting, is embodied in a control of the potential rela tion between the grid and cathode of the nespec' tive device, and such potentialrelation between the grids 33. 43 and the respective cathodes'fl,

the devices H or I8 is non-conducting, a unition' of tIie se list 42 is determined by the resistors 35, 45. If the grid is sufficiently negative relative to its related cathode, it will not conduct and no current flow will take place unidirectional from the anode to the cathode, comprising through that device a .5 pulsating direct current of predetermined direction and potential.

During the increment of rotation of the cams 29, 30 when the galvanometerneedle 23 is in engagement with either the contact 24 or the contact 25, the normal potential relation existing between the'grid and cathode of each thermionic device is modified so that for that increment of time one or the other of the discharge devices will be non-conducting, depending upon l5 whether the needle is in engagement with the contacts 24 or 25. This is accomplished by connecting the galvanometer needle to the grids 35, 40, the contact 24 to the cathode 42 and the contact 25 to the cathode 4|, Due to the relatively high values of the resistances 36, 45, when the galvanometer needle is in engagement with the contact 24 a potential substantially equal to that of the cathode 42 will be impressed upon the grids 39, 40 which will render the discharge de- 5 vice I8 non-conducting during that portion *of the alternating current cycle in which it was normallyconducting previously. The discharge device will, however, remain conducting through one-half of the alternating current cycle as the potential of the grid 39 will be positive. with respect to the cathode 4| when the anode 31 is positive. When the galvanometer needle is in engagement with contact 25, a similar action takes place wherein the discharge device II will be non-conducting throughout the full alternating current cycle.

Now, as explained hereinbefore and more in detail in my co-pending application, when one of directional or pulsating direct current from the conducting device will be impressed across the motor I3 whereby the rotor will rotate in-predtermined direction for a control of the fuel supply valve 3. Such rotation will continue so long as one of the devices l1, l8 remains non-conducting, but the'rotation will stop substantially instantaneously as soon as both the devices i1, 1 H! are made conducting, each for a half cycle of the alternating current wave. Inasmuch as the devices |8 are oppositely connected in parallel and in series with the motor l3, there is applied to the motor I3 a unidirectional pulsating direct current from one of the devices in a direction to cause rotation in one direction, and from the other device in a direction to cause rotation inthe opposite direction. When both of the devices are conducting, a full wave alternating current is impressed across the motor |3 and the equal opposing torques tend to' cance'l, with no'urge tojrot'atlon of the armature." A feature of the invention resides 'in the fact that simultaneously with the control of Hid-m0? tor I3, I have provided ia control "-of he' nioto r 5 whereby the"pulsatin g direct curren passing" throughthe' outputcir vices l1, l3 'is'effecti've current motor "5. Connected in series with the anodes 31,38 are the satur 4] .16!

saturable core reactor 48 and 49, respectively, ,7 c

across the power source l5; f

When, the thermionic discharge'devices 'il If? device IB will be rendered non-conducting. Durand will engage the contact 25 for increments of are both conducting currents, then, due to the well known characteristics of the saturable core reactors, the impedance of the windings 4B, 49 will be 01' a suillciently low magnitude to permit normal and equal energization of thefields 5, 1 whereby the rotor 8 will be not urged to rotation. When, however, either the device I! or the device I! is rendered non-conducting, as previously explained, then the impedance of the saturable coil reactor having its saturating winding connected in series with the anode of the discharge device, will be increased to such a magnitude as to substantially de-energize the field of the motor connected in series therewith. This unbalance oi energization of the fields 6, I will allow rotation of the rotor 8 in predetermined direction for movement of the indicator arm 9 and the slide wire resistance contact arm 20A.

In operation when, as shown, the thermocouple potential is equal to that of the potentiometer circuit or the two are in balance, the galvanometer needle will be in its neutral or mid-position. The thermionic discharge devices l1, l8 will'each conduct alternate half cycles of the alternating current wave, the complete cycle of which will be impressed upon the motor l3, whereby the armature will be not urged to rotation and will remain stationary. The pulsating direct current in the output circuit of the devices l1, l8 will be of sufficient magnitude to maintain the impedance of the saturable coil reactors 48, 49 at a sufilciently low value so that the fields B, I of the motor 5 will be normally energized, thereby balancing opposed forces so that the armature ,8 is not urged to rotation. Upon a de-= crease in temperature, for example, within the furnace, the galvanometer needle 23 will be dis-v of rotation of the shaft 3| proportional to the amount of displacement, the contact 24 will engage the needle 23 and there will be impressed on' the grid 40 a potential substantially equal to the potential of the cathode 42, whereby the ing the increment of time, therefore, that the needle is in engagement with the contact 24 for each cycle of the shaft 3|, a pulsating direct current will be impressed on the armature of the motor l3, eil'ecting rotation in a'direction to increase the temperature at the thermocouple 4.

The motor 5 will likewise rotate during the slide wire resistance 20 to decrease the potential impressed on the galvanometer by the current in the potentiometer to that impressed on the galvanometer by the thermocouple. When,through the movement of the contact arm 20A, these potentials are again in balance, the galvanometer needle 23 will be in the neutral position and there will. be no further engagement between the needle and the-contact 24 until there is a further decrease in the thermocouple potential.

Upon an increase in temperature of the furnace and corresponding increase in thermocouple potential, the-galvanometer needle will be displaced from its mid-position toward the contact 25 an,

amount proportional to the change in potential,

time proportional to the displacement. The resulting positioning of the motor I3 and of the motor 5 will be in the, opposite direction to that.

just described, whereby the control valve 3 will be positioned for a decrease in the temperature of the furnace and the rotor 8 will position the indicator 9 to indicate an increased temperature. Likewise, the contact arm 20A will move in the opposite direction along the slide wire resistance 20.

The accuracy of a potentiometer may bematerially affected through change in the potential drop across the'sllde wire resistance. It is desirable, then, to periodically standardize or compare the potential drop through the slide wire resistance with a standard drop or a difierential of potential of known value. In this connection, I provide a constantlyrotated cam driven at proper speed through gearing 5| from the shaft 3|. The gear ratio may be such that the cam makes, say, one revolution in three or four hours, or of any desired speed.

In engagement with the cam surface 50 is one end of a switch bar 52, pivotally fastened to which are contact fingers 53, 54 and 55, each pivoted separately externally relative to the switch bar 52, in a manner such that reciprocation of the bar 52 through rotation of the cam 50 will cause a vertical reciprocation of one end of each of the contact fingers. Further carrie by the switch bar 52 is a rigid arm 55. Such reciprocation will cause that end of each contact finger to move from one contact to another so that alternately certain circuits are close circuited and at alternate intervals other circuits are close circuited.

I illustrate in Fig., 1 the switch bar 52 in its lowermost travel position wherein 'the contact finger 53 connects the coil 49 with motor field contact 54 connects the coil 48 with motor field 6,

' and contact finger connects the galvanometer 2| with thermocouple 4. In its shown position, the contact finger 5B isnot close circuiting any circuit. 5

Upon rotation of the cam 50 to a position 180 tothat shown in the illustration, the just mentioned circuits are open circuited; contact finger 53 connects coil 49 with the field 51 of an alternating current motor 58, contact arm 54 connects the coil 48 with the field 59 of the motor 58, contact finger 55 connects the galvanometer with a suitable resistance 60 and a standard cell 5|; and the contact arm 56 short circuits the motor l3 to electrically lock the motor in position to prevent movement of the valve 3 during the standardizing operation.

The potential between the junction points 62 and IOA is then impressed on the galvanometer in opposition tothe potential of the standard cell 5|. If these potentials are of an unequal magnitude indicating that the proper current is not in the potentiometer circuit, the galvanometer needle will be displaced from the mid-position in one direction or the other, depending upon the potential preponderating. Under such a condition the galvanometer needle will engage either the contact 24 or 25 periodically for increments of time proportional to the amount of displacement. The motor 58 will be operated during such engagement to move a contact arm 63 along the resistance 22 to vary the current in the potentiometer circuit until a predetermined difference of potential exists between the junctions 62, IDA, when the opposed potentials impressed on the galvanometer needle will be equal in magnitude. By

a thermocouple is dependent not only upon the temperature to which the hot junction is exposed and which temperature it is desired to evaluate, but also upon the temperature of the cold junction. In order that thethermocouple potential impressed on the galvanometer in opposition to the potential due to the current in the potentiometer circuit may be proportional only to variations in the temperature surrounding the hot junction, it is necessary to compensate the thermocouple potential for variations in the cold junction temperature. I utilize a current conducting liquid, such as mercury, to shunt out an amount of resistance in the potentiometer circuit proportional to changes in temperature of the cold junction from a referenceor calibration temperature.

Connected in the potentiometer circuit between the junction IDA and slide wire resistance 20 is a resistance wire 63A passing through a mercury thermometer 54. Usually I prefer'to make the resistance wire 63A of manganin or other similar resistance wire having a negligible temperature coefficient. As is well known upon an increase in temperature the mercury will rise within the thermometer 54 an amount proportional to the increase in temperature, submerging a greater length of the wire 63A. Due to the relatively greater cross sectional area of the mercury, the resistance at that portion of the circuit composed of the mercury and submerged wire maybe considered negligible. It is, therefore, evident that the linear expansion of the mercury, due to variations in temperature, will efiect a variation of the resistance of the potentiometer circuit which, by proper calibration, may be made to exactly compensate for changes in the potential developedby the thermocouple due to variations in cold junction temperature. The resist- In my improved device,

ance wire 53A is preferably placed in the potentiometer circuit as shown between the junction IDA and the slide wire resistance 20, inasmuch as variations in the fall of potential necessary to compensate'for changes in the cold junction temperature may then be made so minute as to have no appreciable effect on the fall of potential through the slide wire resistance 20.

In general, in Fig. '1 I illustrate a positioning type of control; that is, for each temperature at the thermocouple 4 there is a definite p'ositioning of opening of the valve 3. With such a control, the width of regulation, namely, the temperature variation for full range of valve positioning, may be reduced untilsubstantially uniform temperature is maintained within the furnace. I further illustrate and have described in connection with'Fig. 1, the simultaneous periodic utilization of aneff'ect representative of temperature for advising the magnitude of the temperature and for control of the temperature, the periodicity being in the time cycle'of rotation of cams 29,30, 35. i

In Fig. 2, generally, I indicate a similar furadmission'of fuel to the furnace. Herein ,I show,

however not simultaneous recording and control but alternate wherein a switching mechanism is periodically actuated to make the thermocouple 4 efiective, first, to record and then to control, and so forth, alternately. Furthermore, I provide, according to Fig. *2, what I term a floating control tending to always maintain a constant predetermined temperature within the furnace, and I have arranged the circuit in such a manner that I may by hand adjust or change the value of the temperature which'is to be maintained.

The parts depicted in Fig. 2, such as the furnace, the motor I3, the recording and indicating assembly and the feeler mechanism, which are all identical with those similar parts of Fig. 1, I designate by similar reference numerals.

For periodically switching the effect of the thermocouple 4 between recording and control-, ling, I show a continuously rotating cam 65 driven through gear 65 from the shaft 3| of the feeler mechanism, to periodically reciprocate a switch bar' 51. To the switch bar are pivotally fastened contact arms 63, 63, 10, and H, each fixedly pivoted at one end in a manner such that upon reciprocation of. the switch bar 51, the free end of each of the contact arms will move from a lower shown terminal to an upper shown terminal. As illustrated in Fig. 2, the switch bar 61 is in its lowermost position of travel whereby the proper circuits are completed to make effective the pyrometer 4 through the feeler mechanism for recording the temperature of the furnace. When the cam 65 moves to a position wherein the switch bar 61 is in its uppermost position of reciprocation, circuits'are completed for making the thermocouple 4 through the feeler mechanism eiTective for control of the valve 3.

To actuate the motor 5 for advising the value of temperature, I utilize thermionic discharge devices 12, 13 wherein I control the relation of potential between the grid and cathode of either device to make the device conducting or nonconducting, thereby varying the impedance of the primary of the related transformer 14 or 15 to result in a substantial de-energization of either the field 6 or the field 1 whereby unequal opposed torques on the rotor 3 allow the rotor to rotate in desired direction. I have explained this in detail relatiye to Fig. 1, and I have further explained, illustrated and claimed the particular features of this type of control in my copending application, Serial No. 605,267 previously referred to.

During alternate periods of time when the cam 65 has reciprocated the switch bar 61 to its uppermost travel position whereby the thermocouple 4 is effective through the feeler mechanism for positioning the valve 3, I utilizein such control thermionic discharge devices 16, 11. Control of these devices is had through varying the potential relation between the respective grid and cathode for making thedevice conducting or non-conducting, as previously explained. The

other are in series with the armature I3 for impressing upon the armature 13 full wave alternating current when both devices are conducting, or pulsating direct current in desired direction when only one of the devices is conducting and for allowingrotation of the armature II in predetermined direction.

As so -far described, the'arrangement of Fig. 2

compares with that of Fig. 1 except that I alter nately utilize one pair of thermionic discharge devices for the recording means and subsequently alternately utilize a second pmr of discharge devices in connection with the control means. I have not shown herein any arrangement for periodically standardizing the potentiometer circuit as in Fig. l, but it-is to be understood that i a balance.

this may readily be added to the arrangement of Fig. 2, as will be clearly seen.

The arrangement of Fig. 1 and that so far described of Fig. 2 is such that upon a departure of temperature within the furnace from a previ-' ous temperature an unbalance will occur in potential relation of the thermocouple circuit whereupon the feelermechanism and amplifying means will cause a positioning along a slide wire resistance to bring the potential relation to The new position of the slide wire contact arm when balance potential is obtained is an indication of the temperature and simultaneously movement may be efiected in proper direction to control the temperature and tend to bring it back toward predetermined value or the control may be accomplished alternately and periodically relative to the indication. All change in indication or control is, therefore, ac complished responsive toa departure of temperature from a previous temperature. In the arrangement of Fig. 2, I additionally actuate the control responsive to a departure of temperature relative to a predetermined temperature desirably to be maintained.

To explain this in simpler language, I may say that the arrangement of Fig. 1 is such, for

example, thatstable conditions may exist with thetemperature in the furnace at any value between 1500 F; and 1520 F. That is, conditions will stabilize with a certain fuel valve opening and a temperature of 1500 F., or they will become stable with a difierent fuel valve opening and a temperature of 1520 F. or at any intermediate point, there being a definite relation. however, between the range 1500-1520 F. and the full travel of the control valve. Such relationship may be. varied through adjustment wherein width of regulation, namely, 1500-1520 F. for full movement of the valve, may be widened or narrowed, and as such range is narrowed, conditions approach the maintenance of a consta'nt predetermined temperature. However, such condition can never be attained for it would mean an on-ofi or wide open-tight closed control of the fuel valve rather than a throttling control.

sponsive to the departure in magnitude of the- With the arrangement of Fig; 1, if the temperature has been stable at 1500 F. and through some outside cause departs to 1502 F., this change in temperature efl'ective upon the ther mocouple' 4 results in an unbalanced potentialin the thermocouplecircuit and as described the slide wire resistance 28 will be re-proportioned in the potentiometer andthermocouple circuits with simultaneous variation in indication of temperatureand of control of the furnace. Thus.

the action of the complete apparatus is in ac;-

cordance with a departure in magnitude of temperature from a previous magnitude and the variation in indication and control is proportional to the extent of the departure.

In the arrangement of Fig. 2, I additionally arrange that the control alone be positioned refrom a condition of balance to a'new condition is 2 F. while the departure in magnitude of the last temperature from predetermined temperature is 6 F. I utilize the departure having a magnitude of 2 F. to actuate the indicating meansto advise the latest temperature and I utilize it inthe next time cycle of the switch bar 61 to actuate the control motor 13 and I further actuate the control motor l3 in accordance with the value 6 F., departure from-predetermined temperature, namely, 1500 F.

To accomplish this I connect in the circuit additional slide wire resistances l8, l9 proportioned as to their efiective value in the circuit according to the magnitude of temperature deviation from predetermined standard, and by having inserted in the circuit, thus, a bias or unbalance of potential representative of the magnitude of 'departure from predetermined temperature, I do not allow the circuit potential to come to a bal-- ance until this biasing unbalance has been satis-' fled and the temperature has been returned to the standard or desired temperature. Thus, it

will be seen that the unbalance of potential after a deviation of temperature is between the thermocouple potential resulting from the 2 F. departure'as wellas the potential bias of the resistances 18, 19 for the 6 F. departure from predetermined standard; using the temperature stated in the example above.

The thermocouple potential will lee-impressed onthe galvanometer in opposition to that due to the current in the potentiometer circuit as determined by the position of a'contact arm 80 positioned with the valve 3 bythe motor l3 and relative to the slide Wire resistance 8|. The re-. sistances 18, I8 are connected in series with the resistance 8| and are proportioned in the circuit through the positioning relative thereto of contact arms 82, 83 insulated from each other but carried together in positioning by a motor 84 similar to the motor 5, and having opposed windings 85, 86. When the winding 85 is energized, the contact arms 82, 83 will move, for example. to cut into the circuit more of the resistance 18 and out of the circuit more of the resistance 79, while if the field 8B is energized the reverse action will take place.

Connected in series with the resistances l8, l9 and'contact arms 82, 83 are contact arms 81, 88 adapted to be moved simultaneously relative to additional slide wire resistances 88, B9, respectively. I provide thereby a hand means'of varying temperature standards to which the control is to function. The contact arms 81, 88 are carried together by a yoke 9|, through which is screw threaded a screw 82 having a knurled or other handle for turning, whereby the yoke Bl moves, along the screw. The yoke 91 carries a pointercooperating with an index 93 which may be graduated in degrees F. representing the standard or desired temperature to be maintained at the thermocouple, in the furnace.

The slide wire resistance 8| is preferably pro.-

portionedto the potential generated by the thermocouple so that a relatively small range in temperature is eifective for positioning the valve connected to the field 95, one to the field 99, and a neutral connected to the power source ii. If the mercury switch is tilted in one. direction,

circuit will be completed for e'nergization of the field 95, while if it is tilted in the opposite direction', the field 99 will be energized.

. the parts 9, 99, 94 to prevent serious overtravel or- The mercury switch 94 is carried by a iulcrumed arm 95 whose free end bears against a cam surface 99. Thecam 99 is fastened by a set screw 91 to the indicator arm 9 of the measuring means so that the cam may be rotated relative to the pivot point on the arm 9 and held in desired position by the set screw 91. Carried by the cam is a pointer 99 adapted to cooperate with an index 99, the latter rigidly fixed to and carried by the arm 9.

When the pointer arm 9 reads on the index I9 and chart II, the desired standard temperature, for example, 1590 F., the cam 96 and pointer 99 will be so located through the set screw 91relative to the arm 9, that the pointer will indicate on the index the temperature 1590" F. and the mercury switch 94 will be in a mid or neutral position wherein circuit is not closed between the neutral contact and the contact to either the field 99 or the field 99.

. Upon a departure in temperature from the standard 1509 F. temperature, the new temperature will be indicated through the position of the arm 9 and simultaneously cam 99 will have been moved relative to the arm 95 for tilt ing the mercury switch 94 to cause an energization of the field 95 or the field 99 whereupon the motor 94 will position the contact arms 92, 93 for inserting in the potentiometer circuit a proportion of the resistances 19, 19 for biasing the circuit to advise the magnitude of the departure of temperature from the predetermined standard temperature.

During those periods of time as determined by the cam 95 and switch bar 91 when thermocouple 4 is effective for positioning the motor 5,

the mercury switch 94 will be positioned corresponding to magnitude of existing temperature. During the same periods of time, as well as the alternate periods of time, the mercury switch will be eflective for control of the motor 94 so that the motor 94 may be positioned regardless of whetherat that instant the thermocouple 4 is efiective for measuring or forcontrol. The neutral connection to the mercury switch 94, however, is connected through an interrupting switch I99 driven at a uniform reciprocation by the cam I9I geared to the shaft 9i. Such periodic interruption of the circuit to the motor 94 allows for change in the temperature of the furnace in corresponding change in position 'of hunting v I 1 l The unit resistance of the slide wire resistances 99, 99 is relatively great compared to the unit resistance of the slide wire 9I so that by moving the contact arms 91, 99 from one extreme position to the other along the related resistances, the potential due to the current in the potentiometer circuit will beyaried an amount equivalent to the potentials generated by the thermocouple over the entire range of predetermined temperatures it may be desired to maintain within the iurnace. If it is desired to change the predeterminedor standard furnace temperature to which the control'is to work, it is only necessary for the operator to turn the screw thread 92 until the pointer ofthe yoke 9| is adjacent the graduation on the index 99 representing the new desired standard temperature. This operation will so vary the potential impressed on the galvanometer by the potentiometer circuit through the resistances 99, 99 that the galvanometer needle will be displaced from its mid-position, effecting a change in position of valve 9 to bring the temperature to the desired new value, when the thermocouple potential will again be equal to that impressed on the galvanometer by the potentiometer current and the galvanometer needle will again be in its mid-position. Thereafter, slight deviations in the furnace temperature will eiiect relatively large movements of the valve 9 through a balancing of the resistances 9|, 19, 19. It is, of course, essential that if a new temperature standard is set up through the hand adjustment 92, the set screw 91 be loosened and the cam 99 and pointer 99 be moved until the pointer 99 reads the same temperature on the index 99 when the pointer arm 9 reads the corresponding temperature on the index I9.

In'control systems of the present character, in order that the temperature within the furnace may be maintained within certain-limits of a desired temperature, and that upon departure from desired temperature the control acts speedily enough to return the temperature without undue lag, it is usually desirable to have the valve 9 move from one extreme position to the other'through a considerably smaller range in temperature than the range of the index I9.

in order to protect the valve 9 and its motor I9 from injury through the motor urging the V valve beyond its maximum open or closed position, to prevent de-energization of one or the other of the fields, whichever would tend to operate the motor to move the valve beyond the extreme open or closed position. It is further desirable to render the galvanometer 2| less sensitive to the differences in potential impressed upon it by the current in the potentiometer circuit and the thermocouple so that the galvanometer needle 29 will not be injured by striking'hard against the contacts 24, 25.

I show in Fig. 2 a limitto the travel of the valve 9 through breaking a circuit at predetermined points in the valve travel which prevents other than the normal potential relation existing between the grid and cathode of the discharge device, which upon being rendered nonconducting would efl'ect rotation of the motor to carry the valve past an extreme position. I render the galvanometer less sensitive to the differences in potential impressed upon it by connecting in series with the thermocouple at the same predetermined point in valve travel, a suitable resistance which, while not afiecting the accuracy of the galvanometer, will decrease its rate-0f response to diflerences in potential so that the needle 29 will remain within desired limits of travel regardless of deviation of the actual temperature beyond the control range.

Positioned with the valve 9 is a cross-piece of the contact arm 99 insulated therefrom and which I designate at I92 adapted at one extreme of travel of the valve 9 to engage a pivoted springurged yoke I99, and at the other extreme of travel a similar yoke I94. When either of the yokes I99, I94 is engaged by an extension of the cross arm I92, the yoke is moved until certain circuits are opened. whereby the movement ceases and no further movement in the same direction of travel may be made.

The yoke I99 is adapted upon engagement of When such is desired, it is necessary, however,

the arm I02 to break circuit, with contacts I08, I insulated from each other and from the yoke. correspondingly, the yoke I04 is adapted to break contacts I01, I00.

Contacts I00, I01 control the making non-conducting of devices 10, II. regardless of engagement between the contact needle 20 and contacts 24, 20. If, for example, contact I00 is opened through rotation of the motor- I0 to an extent whereby I02 engages the yoke I00 and lifts same to open circuit the contact, then the corresponding device I0 is prevented from becoming nonconducting. It will be remembered that if the device 16 is non-conducting, the motor will'rotate in a given direction. If the device I6 is prevented from becoming non-conducting, then the motor can be made to rotate only in a direction opposite to that which will result in an opening of contact I06 and regardless of the engagement of galvanometer needle 20 with contact 24. Correspondingly, should I02 cause an open circuitin of contact I01, the motor II will be allowed to rotate only in a direction opposite to that tending to open contact I01. Thus, the contacts I01, I00 provide limit switches for travel of the motor I0.

I have shown in the thermocouple lead to the contact arm 00a resistance I00 normally short circuited by the contacts I05, I00 connected in series with each other. Should, however, the valve 0 reach an extreme position of travel in either direction, then either the contact I or the contact I00 will be open'circuited', rendering effective the resistance I00. Thereafter, during the time period when the thermocouple is associated with the slide wire resistance 0|, the current effecting displacement of the galvanometer needle 20 from its mid-position will be impeded by the resistance I00 sufliciently so that before the galvanometer needle has passed beyond desirable limits of travel it will be clamped between the bars 00, 04. While the resistance I00 serves to render the galvanometer less sensitive to differences in potential impressed upon' it, .the accuracy of the galvanometer will not be affected, and furthermore, as soon as the temperature within the furnace returns within the control range, closing the broken circuits I05 or I00, then the galvanometer will be restored to its normal sensitivity until there is a further variation in temperature beyond the control range.

Inherent characteristics of metallurgical furnaces similar to the one Ihave illustrated may vary widely, depending upon siz'e, construction, method of firing and so forth. In some furnaces, to increase the rate of fuel feed a predetermined amount would effect a substantially instantane ous increase in the furnace temperature, whereas in other furnaces a considerable interval of time would elapse before a given change in the rate of fuel feed would affect the furnace temperature. A control system having for its object to maintain a predetermined temperature within the furnace, must take into consideration the rate of response of the particular furnace, otherwise a himting condition will be set up causing the temperature to periodically go above or below the desired value. The rate of changeof supply of fuel must, therefore, be established according to the rate of response of the furnace.

In order that the rate of response of a particular furnace may be satisfied to agree with the inherent characteristics of the furnace, I show a resistance III connected in series-with a thermocouple, and the effectiveness of which may be varied by manual manipulation of the contact .arm III. The characteristics of the resistance II. are similar to those of the resistance I00 in that it is eifectivc for changing the responsiveness of the gaivanometer to differences in the opposed potentials impressed upon it. If, for example, the time lag-of the particular furnace to which the control system may be applied is.

negligible, the galvanometer'may be made practically instantaneously responsive to diiIerences in potential by moving the contact arm III counterclockwise to the extreme position, shuntingoutallofthe resistance IIII.

If, however, considerable time lag exists between a change in the rate of fuel supply and a variation in furnace temperature, any degree of responsiveness of the galvanometer may be obtained by rendering effective more or less .of the resistance IIO through movement of the contact arm II I. Inasmuch as the galvanometer needle 20 is periodically at stated intervals of time clamped between the bars 00, 04, it is evident that its displacement from the mid-position at the instant it is clamped will not only be proportional to the difference in actual valve position from thedesired position, but also to the amount of the resistance III rendered effective by the position of the contact arm III, so that while periodically, and as described, the motor I 0 will be operated to position the valve 0, the increment of time that" the motor is operated and consequently the increments of motion of the valve will be less in proportion to the amount of. resistance I III effective. Eventually, however, the valve will open or close the same amount and change the rate of supply of fuel proportionally for a given change in temperature, regardless of the amount of resistance connected in the thermocouple lead.

While I have illustrated the invention as relating particularly to the measurement of temperature and the use of thermocouples, still I contemplate that the arrangement may be utilized for the measurement and control of other variables or characteristics in the operation of apparatus and which may be of a physical, chemical, thermal, electrical or other nature; Such variables might be flow, temperature, pressure or ratio of variables, and so forth.

While in the description and the appended claims for the sake of simplicity and clearness I have used. the terms "slide wire resistance" and "slide wire potentiometer, it is to be understood that I include in this term any variable resistance capable of performing the same-function.

Certain other types of feeler and amplifyingmechanisms maybe utilized, as well as electromagnetic means other-than the motors I have shown. While I have illustrated and described certain preferred embodiments of my invention, I

it is to be understood that I am not to be limited thereby except as to the claims in view of prior art.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

1. In a temperature measuring and controlling apparatus, the combination of, a heating furnace, means for supplying an element of combustion to the furnace, regulating means for such supplying means, an indicator of the temperature of the furnace, an alternating current motor for positioning the indicator, a second motor having a separately direct current excited field and an armature connected in an alternating 'currenl circuit for positioning the regulating means, thermionic discharge devices for energizlng the motors, and means responsive to temperature for controlling the thermionic discharge devices.

2. In a temperature regulator, the combination with a heated apparatus, of means for supplying heat thereto, regulating means for said heating means, a motor having an armature and a separately direct current excited field for operating said regulating means, a source of alternating current for energizing the armature, control means for said motor comprising two-electron discharge devices, each having a grid, a cathode,

and an anode, the output circuits oi the electron discharge devices oppositely arranged in parallel and connected with said armature, means for maintaining a normal potential relation between said grid and cathode, and temperature sensitive means for changing such relation.

3. In a temperature regulator, the combination with a heated apparatus, of means ior'supplying heat thereto, regulating means for said heating means, a motor having an armature and a separately direct current excited held for operatingsaid regulating means, a source or alternating current for energizing the armature, control means for the motor comprising two electron discharge devices, each having a grid, a cathode, and an anode, the output circuits of the electron discharge devices oppositely arranged in parallel and connected with the armature, means for maintaining a normal potential relation between said grid and cathode, and temperature sensitive means for periodically changing said relation for increments of time proportional to variations in the magnitude of the temperature of said apparatus.

4. In a temperature regulator, the combination ,with a heated apparatus: of means for supplying heat thereto, regulating means for said heating means, a source of alternating current for energizing said regulating means, control means for the regulating means comprising two electron discharge devices, each having a plate, a-grid, and a cathode, the plates and cathodes of the devices oppositely connected in parallel and in series with said regulating means, means for maintaining-.a

normal potential relation between the grids and' cathodes oi. said devices, and means sensitive to the temperature of saidheating apparatus for changing such relation.

5. In a temperature regulator, the combination with a heated apparatus, of means for supplying heat thereto, regulating means for said heating means, a motor having an armature and a separately direct current excited field for operating said regulating means, a source of alternating current for energizing the armature, control means for said motor comprising two electron discharge devices having input and output circuits, the output circuits of the devices oppositely connected in parallel and the armature of the motor connected in the output circuit; and means responsive to the temperature of said apparatus tor controlling the energization of the input circuits.

6. In an apparatus for measuring and controlling the magnitude or a variable, the combination of means sensitive to variations in the magnitude of the variable, a pair of electron discharge devices each having a cathode, a grid and a plate,

arranged oppositely in parallel, a motor having an armature and a separately direct current excited field, the armature oi the motor connected in the plate circuits of said electron discharge devices, regulating means operated by said motor,

an alternating current motor having opposed fields and connected in circuit with said electron discharge devices, a source of alternating current for energizing the armature of the first named ,motor and the opposed fields of the last named motor, means for maintaining a normal potential relation between the grids and cathodes of said electron discharge devices and means sensitive to variationsin the magnitude of said variable for changing said relation.

'7. The combination with a plurality of circuits, of a movable, member, a plurality of independently energized electromagnetic windings for exerting opposed forces on said movable member, each of said windings connected in one of said circuits, 8. second plurality of circuits, a source of alternating current for energizing said first and. second named plurality of circuits,

- means for controlling the current in said second named circuits, and a saturable core reactor coupling each ofsaid first named circuits with .one of said second named circuits.

8. The combination with a plurality of circuits,

of a motor .having a rotor and opposed independently excited windings, each of said windings ,connected in one of said circuits, a secondplurality of, circuits, a source of alternating current for energizing the first and second plurality of circuits, means for controlling the cur'rent in said second named circuits, and a saturable core reactor couplingleach of said first named circuits with one of said second named circuits.

9. The combination with a. galvanometer having a member adapted to be'deflected in opposite directions, or a thermocouple, a potentiometer comprising a source of current and a slide wire resistance, a movable contact arm adapted to be positioned along the slide wire resistance, a connection from said contact arm to said thermocouple, a connection from the galvanometer to the thermocouple, a connection from the .potentiometer circuit to the galvanometer, said thermocouple and potentiometer cooperating to control the galvanometer, a resistance connected in series with the thermocouple, a normally closed shunt circuit around said resistance and aswitch member actuated by said contact arm at predetermined points in its travel to open said shunt circuit.

10. The combination with a potentiometer'circuit comprising a source or current and a slide wire resistance, of a second resistance in said circuit and means sensitive to an independent variablefor short circuiting varying amounts of. said last named resistance proportional to variations in the independent variable.

11. The combination .with means for producing an electrical efiect bearing a functional relation to the difference in magnitude of two independent variables, of a potentiometer for determining the magnitude of one of the independent variables comprising a source of potential, a slide wire resistance, a second resistance, and means for automatlcally'varyin'g the drop in potential through the last named resistance in accordance with variations in the'magnitude oi. the other of said independent variables;

12. The combination with a thermocouple for producing apotential, of a potentiometer for measuring said potential comprising a current source, a slide wire resistance, a second resistance; and means for automatically short circuiting'a portion of said last named resistance- 13. The combination with a thermocouple for producing a potential, 0! a potentiometer for measuring said potential comprising a current 1|.

source, a slide wire resistance, and means tor automatically compensating for variations in the cold junction temperature of said thermocouple, said last named means comprising a resistance and means tor-automatically short circuiting a portion 01 said last named resistance.

14. The combination with a thermocouple for producing a potential, 01' a potentiometer for measuring said potential comprising a current source, a slide wire resistance, and means for automatically compensating for variations in the temperature oi the cold junction of said thermocouple, said last named means comprising a resistance and means for automatically short circuiting an amount of the last named resistance bearing a functional relation to changes in cold junction temperature.

15. The combination with a thermocouple for producing a potential, of a potentiometer for measuring the potential comprising a current source, a slide wire resistance, and means for automatically compensating for changes in the temperature of the cold junction of said thermocouple, said last named means comprising a resistance and means responsive to variations in temperature ior automatically short circuiting portions of said resistance, the tall of potential through said resistance compensating for variations in temperature.

' 16. In an apparatus for measuring and controlling the magnitude oi a variable, the combination of means sensitive to variations in magnitude of the variable, an electron discharge .device electrically controlled thereby, means for regulating the magnitude 01' said variable cona heated apparatus, the combination of means sensitive to variations in temperature within said apparatus, an electron discharge device electrically controlled thereby, means ior regulating the magnitude of the temperature controlled by the current in the output circuit of the electron discharge device, a device for advising the magnitude oi the temperature, a source of current for energizing said device, and a saturable core reactor coupling the output circuit of said electron discharge device with'the circuit of said device.

18. In a temperature measuring device, the combination of means sensitive to variations in temperature, an electric circuit, means under the control 01! said temperature sensitive means for regulating the current in said circuit, another circuit, electromagnetic means for operating said measuring device connected in said last-named circuit, and a saturable core reactor connecting.

said first and second-named circuits.

19. Control apparatus comprising a deflecting member, a direct-current motor having an armature and a separately excited ileld, an electric circuit for the armature of said motor, means cooperating with said deflecting member for normally energizing said circuit with alternating current, and for selectively energizing said circuit with direct-current in one direction, or with direct-current in the opposite direction periodically ior increments of time proportional to the amount or deviation of said deflecting member from a given position.

20. The combination with a device having a condition to be-controlled, of means responsive to said condition, an electron discharge device, regulating means for an agent supplied said device for producing or maintaining said condition controlled by the space current in said electron discharge device, another electron discharge device, indicating means controlled by the space current in said second-named electron discharge device, said first-named electron discharge device electrically controlled by said first-named means during alternate periods of time, and said second-named electron discharge device electrically controlled by said first-named means durin periods succeeding such alternate periods.

21. The combination with a heated device of means responsive to the temperature thereoi', an electron discharge device, regulating means for a heating element. supplied said heated device controlled by the space current in said'electron discharge device, another electron discharge device,

' indicating means controlled by the space current in said second-named electron discharge device, said first-named electron discharge device electrically controlled by said temperature responsive means during alternate periods, time, and said second-named electron discharge device controlled by said temperature responsive means during periods succeeding said alternate periods.

22. Iii-combination, a heated device, a thermocouple responsive to the temperature within said device, automatic mechanism comprising a galvanometer having a movable member responsive to variations in the potential generated by said thermocouple and a periodically reciprocated arm adapted to engage said member for increments oi time bearing a functional relation to the deflection of said member from a neutral position,

an electron discharge device having an input and an output circuit, means connected in said output circuit for controlling an element of combustion to said i'umace, a second electron discharge device having an input and an output circuit, an indicator connected in the output circuit of said second-named electron discharge device, and means whereby said automatic mechanism electrically controls the first-named electron discharge device during alternate periods of time, and electrically controls the second-named electron discharge device during periods succeeding each alternate period.

23. In combination with a heated device and means for supplying a heating element thereto, means ionproducing a potential representative of the temperature of said device, means for producing a potential representative of the rate of supply of said heating element to said device,

means for regulating the rate of supply of said heating element, control means for said regulating means comprising an electric motor, a plurality of electron discharge devices, said motor controlled by the space current throughsaid devices, an indicator, means for producing a potential representative of the position of said indicator, operating means for said indicator'comprising an electric motor, a second plurality of electron discharge devices,-sa-id last-named motor controlled. by the space current through said second plurality of electron discharge devicesf and means for controlling, during alternate periods, the input circuits of said first-named electron discharge devices in accordance with the diil'erence between the potential representative of 1 2 v the temperature of said device and the potential representative oi the rate oi supply of said heating element,'and during periods succeeding said alternate periods controlling the input circuit of said second plurality of electron discharge devices in accordance with the diiierence between the potential representative of the temperature of said device and thepotential representative of the position 01' said indicator.

24. In combination with a heated device and means for supplying a heating element thereto, means for producing a potential. representative oi the temperature of said device, means for producing a potential representative of the rate of supply of said heating element to said device, means for regulating the rate 01 supply of said heating element, control means for said regulating'means comprising'an electric motor, a plurality' oi. electron discharge devices, said motor controlled by the space current through said devices, an indicator, means for producing a potential representative oi the position or said .indicator, operating means for said indicator comprising an electric motor, a second plurality of electron discharge devices, said last-named motor controlled by the space current through said second plurality of electron discharge devices, and means for controlling, during alternate pe-r riods or time, the input circuit of said first-named electron discharge devices in accordance with the diflerence between the potential representative of the temperature oi. said heated device and the potential representative of the rate of supply of said heating element modified in accordance with the temperature within said device, and during periods succeeding said alternate periods controlling the input circuit of said second plurality oi electron discharge devices in accordance with the diflerence between the potential representative of the temperature of said device and the potential representative of the position of said indicator.

25. In combination with a heated device and means for supplying a heating element thereto, means for varying the supply of said heating element, regulating means iorsaid last-named means comprising an electric motor, a plurality of electron discharge devices, said electric motor controlled by the spacecurrent' through said electron discharge devices, means for electrically controlling said electron discharge devices to maintain a practically iixed' ratio between the rat? oi supply of said heating element and the temperature '01 said heated-device, and means for modifying the control of said electron discharge lasttnamed temperature.

. variable, comprising in combination, an indicator of the variable, means sensitive to the value of the variable, an electric circuit, means under the conti'ol'oi said sensitive means for regulating the current in said circuit, another circuit, electromagnetic means i'or positioning said indicator and connectediin said last named circuit, and a saturable core reactor connecting said first and second named circuits.

2'7. In an electrical control system including a source of alternating current: the combination with two reactors, each having a core of variable magnetic permeability and two independent mas,- netizing windings thereon; of 'a' network adapted to .receive energy from the alternating current source, a motor to receive energy irorn said network, the said one independent winding oi each devices in accordance with the magnitude of saidnetwork, means adapted to be included in series of the other said independent windings of each of the said reactors, and means responsive to a condition to be controlled and adapted to effect changes in the flow '0! said direct-current energy.

28. Electrical measuring and/0r control system, comprising a source of alternating current, a reactor member having a circuit connected thereto, a magnetizing circuit associated with the reactor, means adapted to be included in series with the magnetizing circuit and subject to a variable condition for-magnetizing directly the reactor member, and means connected with the reactor circuit for measuring and/or controlling the said condition.

29. Means for adjusting the slide wire in a potentiometer system having a. galvanometer, comprising an electric motor; a variable connection to the slide wire operated by the motor; a motor control circuit including a contact controlled by the galvanometer; a cooperating contact. nor mally incapable of engaging the contact moved by the galvanometer; and means operated independently oi the galvanometer for causing said contacts to be pressed into firm engagement intermittently, said motor control circuit including a thermionic device, the grid circuit of which is controlled by said cooperating contacts.

30. Means for adjusting the slide wire in a potentiometer system having a galvanometer, comprising an electric motor; \a variable connection to the slide wire operated by the motor; and

means periodically made operative and at each operation causing the motor to move said variable connection a greater or lesser extent in one direction or the other and controlled by the. galvanometer in its oil-zero movements and depending upon the magnitude and direction of said oil-zero movements, said last-named means comprising a pair of thermionic devices, each for controlling one directional movement of the variable connection.

31. In an electrical control system including a source of alternating current, the combination with two reactors, each having a core oi variable magnetic permeability and'two independent magnetizing windings thereon, of a network adapted to receive energy from the alternating current source, a motor to receive energy from said network, the said one independent winding of each of the plurality or reactors towing a part of said network, a second network adapted to receive energy from the alternating current source, "the other of said independent windings of each of theplurality'oi reactors forming a part oi the second network, and means for controlling the current in the second-named network, said reactors coupling the networks.

32. The combination with a plurality of circults, of a motor having a rotor and a plurality oi field windings, each of said windings connected in one of said circuits, a source of alternating current Ior'energizing said circuits, 9. second plural ity of circuits, an electron discharge device in each 01 said second plurality of circuits, and a saturable core reactor coupling each oi said firstnamed plurality of circuits with one of said second-named plurality oi. circuits. 33. Apparatus for controlling the value of a variable, comprising in combination, a controller for the variable, means sensitive to the value of the variable, an electric circuit, means under the control oi said sensitive means for regulating the I current in said circuit, a second electric circui said controller responsive to current variations in one of said circuits, and a saturable core reactor connecting said first and second named circuits.

34'. The combination with a plurality 'oi circuits, of a movable member, a pluralityof independentlyenergized electromagnetic windings for exerting opposed forces onsaid movable member,

each of said windings connected in one of said circuits, a second plurality of circuits, a source of alternating current for energizing saidfirst and second named plurality of circuits, means for controlling the current in said second named circuits, and an impedance coupling device coupling each of said first named circuits with one of said second named circuits.

35. The combination with a plurality of circuits, of a motor having a rotor and opposed independently excited windings, each of said windings connected in one 01! said circuits, a second plurality of circuits, 2. source of alternating current for energizing the first and second plurality of circuits, means for controlling the current in said second named circuits, and an impedance coupling device coupling each of said first named circuits with one of said second named circuits.

36. In combination, a source of alternating current, a plurality of reactors having magnetic circuits of variable permeabilities, windings thereon adapted to provide reactance in the source of alternating current, and further magnetizing windings, energizing circuits for said last ,men-

} tio'ned magnetizing windings and sources of unidirectional current to energize the same, whereby 1 the magnetic circuit of one of said reactors may receive unidirectional excitation independently of another, together with means including a switch and actuating means therefor operative in response to a variable condition for controlling said unidirectional excitation, and an electro-responsive device adapted to receive energy from said source of alternating current in a degree governed by the magnitude of said controllingunidirec tional excitation.

37. In an electrical control system including a source 01' alternating current, the combination withtwo reactors, each having a core oi variable magnetic permeability and two independent magnetizing windings thereon; of a network adapted to receive energy from the alternating currentsource, a motor to receive energy from said network, the said one independent winding of each of-the plurality of reactors forming a part or said network, unidirectional current sup- 13 ply means adapted to be included in series with each of the other of said independent magnetizing windings and to selectively deliver directcurrent energy alternatively to one or the other of the other said independent windings of each of the said reactors, and means responsive to a condition to be controlled and adapted to effect changes. in the flow of said unidirectional-current energy. 7

38. In an electrical control system including a with two reactors each having a core of variable magnetic permeability and two independent windings thereon; of a network adapted to receive energy from the alternating current source, a motor to receive energy from said network, the said one independent winding of eachof the plurality of reactors forming a part of said network, unidirectional-current supply means adapted to be included in series with each of the other oi'said independent magnetizing windings, and a double-throw switch operativelyassociated with thesourcesof unidirectional-current supply and saidilast mentioned magnetizing windings and eifective to control the flow of energy to one or the other of the other of said independent windings of each or said reactors, and means responsive to a conditionto be controlled to effect the actuation oi'said switch.

39. Electrical measuring and/or control system, comprising a source of alternating current, a rea'ctor member having a circuit connected theresource 01' alternating current, the combination to, a magnetizing circuit, means including a switch and actuating means therefor operative in response to a variable conditionfor magnetizing directly the reactor member, andmeans connected with the reactor circuit for measuring and/or controlling the said condition.

40. Means for adjusting the slide wire in a potentiometer system having a galvanometer,

motor control circuit including'cooperating contacts, means actuated by said galvanometer for relatively moving one of said contacts while maintaining said corresponding contacts in spaced relation, and means operated independently of the galvanometer for causing said contacts to' be pressed into firm engagement intermittently, said motor control circuit including a thermionic device, the grid circuit of which is controlled by said JQHND. RYDER."

cooperating contacts.

x 4D comprising an electric motor; a variable connection to the slide wireoperated by the motor; a 

